Coated fibers and process

ABSTRACT

This unique processing provides a unique mixture for coating reinforcements. Preferably, the mixture is an epoxy/polystyrene mixture developed for coating glass fiber reinforcements for thermoset resins such as polyesters. My processing threads a glass fiber roving through a series of threaders, eyelets and brakes. The glass then is coated and dried. After drying, the roving then is wrapped around chilled mandrels and chopped into an appropriate length. The coating is critical to the performance and cosmetic appearance of the part (molded product). The fiber after processing then is introduced into the resin matrix. The processing strips or shears the after coating from the fiber prior to molding.

TECHNICAL FIELD

[0001] This invention relates to a process for producing reinforcements for reinforcing plastics. The processing produces unique coated fibers that remain in suspension in a resin premix for an indefinite period of time.

BACKGROUND OF THE INVENTION

[0002] Fiber reinforced plastics (FRP) involve many types of fibers, matrix polymers, such as thermoplastics and thermosets, and various processes to produce them. In these processes, variations occur in the manner and time of adding the reinforcement. For instance, molding of thermoplastic objects and parts involves one of two process routes. One approach is the combination of the fibers and the matrix thermoplastic polymer to produce a fiber reinforced pellet of the matrix polymer, which is subsequently molded. The other approach involves combining the fibers and matrix polymer just prior to a molding operation. The production of fiber reinforced thermosets combines the fiber reinforcement and thermosettable matrix resin in a partially cured state as in bulk molding compound or sheet molding compound that is capable of further curing upon molding.

[0003] Finding a coated fiber reinforcement which eliminates the partially cured state of the thermoset resin in the BMC or SMC would be highly desirable.

BRIEF SUMMARY OF THE INVENTION

[0004] In a disclosed embodiment of this invention, glass fibers are coated with a coating that prevents the fiber from reacting or reinforcing a plastic matrix. The coated fibers are then mixed into the plastic matrix. Since the coating prevents interaction, the fibers can be mixed into the plastic matrix and then transported to a molding location. Thus, the restrictions as mentioned above are eliminated. The plastic matrix including the coated fibers is passed through a mixing station on the way to a mold. The mixing station is preferably provided with rotating screw members which crack the coating. Once the coating is cracked or otherwise broken, then the reaction (curing) and reinforcing as mentioned above will begin. However, the mixed plastic and fibers are then being immediately delivered to the mold where curing and reinforcing may take place.

[0005] Any type of coating which will delay the fiber being able to cure in its plastic matrix would be within the scope of this invention. Particular coating agents include epoxylated phenolics, epoxylated carboxylic acids, polymers of unsaturated epoxides, epoxidated dienes or polyenes, polystyrene and mixtures of any of the foregoing.

[0006] Preferably, this invention provides a unique epoxy/polystyrene mixture for coating the reinforcements. Preferably, the epoxy/polystyrene mixture was developed for coating glass fiber reinforcements for thermoset resins such as polyesters. My processing threads a glass fiber roving through a series of threaders, eyelets and brakes. The roving traveling at 2-14 feet per second then is coated with the epoxy-polystyrene mixture. The glass roving now coated then is dried using a standard high intensity I.R. oven or UV drying. After drying, the roving then is wrapped around chilled mandrels (−20° F.) and chopped into an appropriate length. Preferably, the chilling is at temperatures below freezing. The coating type and thickness is critical to the performance and cosmetic appearance of the part (molded product). The roving after processing then is introduced into the resin matrix in a ribbon blender. Downstream, a turbine mixer shatters or shears the coating from the chopped roving for uniformly and mechanical strength. The feet per minute of the matrix through the output lines, temperature of matrix, turbine pitch and RPM all influence the products integrity and appearance. The coating is shattered or sheared off the chopped rovings without further breaking the chopped rovings. The coating then dissolves into the resin matrix.

DETAILED DESCRIPTION OF THE INVENTION

[0007] The epoxy/polystyrene mixture of this invention includes a water soluble, dispersible or emulsifiable epoxy polymer. Essential to the present invention is that the glass fibers are coated with a coating agent selected from epoxylated phenolics, epoxylated carboxylic acids, polymers of unsaturated epoxides, epoxidated dienes or polyenes, and mixtures of any of the foregoing.

[0008] Examples of these types of surface-coatings include bisphenol A-type epoxy compounds obtained by reacting bisphenol A with epichlorohydrin, epoxy compounds obtained by reacting 4,4′-dihydroxydiphenylmethane with epichlorohydrin, poly(alkylene ether glycol diglycidyl ethers) such as polyethylene glycol diglycidyl ether or polypropylene glycol diglycidyl either, alkylene glycol diglycidyl ethers such as ethylene glycol diglycidyl ether or butanediol-1,4-diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, vinyl cyclohexane dioxide, dicyclopentadiene dioxide, 3,4-epoxy-6-methylcyclohexyl-methyl-3,4-epoxy-6-methyl-cyclohexane carboxylate and novalac-type epoxy compounds derived from a novolac resin and epichlorohydrin or similar compound. These epoxy compounds can be used either alone or in combination with one another.

[0009] The epoxidized novalacs are obtained from reaction of novalac resins with epihalohydrins such as epichlorohydrin. Typically, the novalac resins are produced by reacting phenol; ortho, meta, and/or paracresol or polyhydroxylated benzene compounds such as resorcinol, with a formaldehyde or aldehyde compound or carbonyl-containing compounds in the case of resorcinol in acid solutions. The epoxy novalacs contain from about 2 to 6 phenolic hydroxyl groups and have epoxy functionalities of from about 2 to about 5.

[0010] The epoxy equivalent weight is the weight of the resin in grams which contains one gram equivalent of epoxy functionality. Any procedure known to those skilled in the art may be used for determining the epoxy equivalent weight. The epoxy equivalent weight of the epoxy novalac resins can be any value which permits emulsification or dispersion of the epoxy novalac polymer in water at least with the use of an organic cosolvent. The epoxy novalac emulsion can be prepared by any method known to those skilled in the art using appropriate types and amounts of nonionic, cationic, anionic and/or amphoteric emulsifiers which are compatible with the epoxy polymers. I prefer that acid pH emulsifiers be used.

[0011] The polystyrene of this invention means polymers of homopolystyrene and its copolymers. Representative comonomers are acrylonitrile, butadiene, α-methyl styrene, methacrylate, dimethyl styrene and the like. Examples of copolystyrenes are acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, high-impact polystyrene resin, and mixtures of the above resins with other resins.

[0012] Convention coats or sizes individual glass filaments during forming directly below the bushing or other forming means. I apply the after coatings of this invention onto strands, yarns or rovings made of a plurality of filaments. My aftercoating forms a sheath around the bundle of the roving or the like. Naturally, some penetration into the filaments of the bundle occurs. During turbine mixing with the resin components, the mixing blades shatter or shear the coating from the chopped roving without breaking the bundle.

[0013] The amount of the glass fibers coated with the epoxy/polystyrene mixture of this invention is 5 to 65% by weight, and particularly preferably 20 to 50% by weight, based on the weight of the composition. The glass fibers may be in any shape, either long fibers or short fibers as long as the mixture can be coated on to the surface of the glass fibers.

[0014] The polyester comprises the polycondensation reaction product of one or more dihydric alcohols and one or more ethylenically unsaturated polycarboxylic acids. By polycarboxylic acid is generally meant the polycarboxylic or dicarboxylic acids or anhydrides, polycarboxylic or dicarboxylic acid halides, and polycarboxylic or dicarboxylic esters. Suitable unsaturated polycarboxylic acids, and the corresponding anhydrides and acid halides that contain polymerizable carbon-to-carbon double bonds may include maleic anhydride, maleic acid, and fumaric acid. A minor proportion of the unsaturated acid, up to about forty mole percent, may be replaced by dicarboxylic or polycarboxylic acid that does not contain a polymerizable carbon-to-carbon bond. Examples of which include O-phthalic, isophthalic, terephthalic, succine, adipic, sebacucm methyl-succinic, and the like. Dihydric alcohols that are useful in preparing the polyesters include 1,2-propane diol (hereinafter referred to as propylene glycol), dipropylene glycol, diethylene glyco, 1,3-butanediol, ethylene glycol, glycerol, and the like. Examples of suitable unsaturated polyesters are the polycondensation products of (1) propylene glycol and maleic and/or fumaric acids; (2) 1,3-butanediol and maleic and/or fumaric acids; (3-combinations of ethylene and propylene glycols (approximately 50 mole percent or less of ethylene glycol) and maleic and/or fumaric acid; (4) propylene glycol, maleic and/or fumaric acids and dicyclopentadiene reacted with water. In addition to the above described polyesters one may also use dicyclopentadiene modified unsaturated polyester resins described in Pratt et al., U.S. Pat. No. 3,883,612.

[0015] The acid number to which the polymerizable unsaturated polyesters are condensed is not particularly critical. Polyesters which have been condensed to acid numbers of less than 100 are generally useful, but acid numbers less than 70 are preferred. The molecular weight of the polymerizable unsaturated polyester may vary over a considerable range, but ordinarily those polyesters have a molecular weight ranging from 300 to 5000, and more preferably, from about 500 to 5000.

[0016] The monomer component comprises materials that copolymerize with the unsaturated polyester. The olefinically unsaturated monomer that is copolymerizible with the unsaturated polyester is most generally styrene, however, methyl-styrene or methyl methacrylate also are useful. In preferred embodiments, the monomer is present in amounts ranging from 25 to 65 percent, by weight, based on the total weight of the system. Especially preferred concentrations of monomer are in the 35 to 50 percent, by weight range.

[0017] Peroxide catalysts such as benzoyl peroxide, methyl ethyl ketone peroxide and cumene hydroperoxide are usually added to the polyester resin to effect curing. A number of other peroxide catalysts such as cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide, bis(para-bromobenzoyl) peroxide, and acetyl peroxide, are also used.

[0018] The polyester contains an amount of blowing agent. Blowing agents may be physical (inert) or reactive (chemical) blowing agents.

[0019] Physical blowing agents are well known to those in the art and include a variety of saturated and unsaturated hydrocarbons having relatively low molecular weights and boiling points. Examples are butane, isobutane, pentane, isopentane, hexane and heptane.

[0020] The most commonly used physical blowing agents, however, are currently the halocarbons, particularly the chlorofluorocarbons. Examples are methyl chloride, methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, chlorotribluoromethane, chlorodifluoromethane, the chlorinated and fluorinated ethanes,isocyanate, and the like.

[0021] Chemical blowing agents are generally low molecular weight species which react to generate carbon dioxide. Water is one practical chemical blowing agent. Air, nitrogen, argon and carbon dioxide also may be used.

[0022] The coatings on the rovings may be as high as 15% by weight. Typically, the amount ranges from 5 to 10 percent by weight. Actual examples were prepared at 7% and 9% by weight.

[0023] The coating composition of this invention primarily is used for glass fibers and strands. The invention also may be used on filamentary material such as thermoplastic synthetic fibers like polyesters, nylons, and cellulose acetate. I prefer to apply the composition to the glass fibers well after their formation when the glass fibers are in the form of strands, yarns or rovings. The glass fibers on which the composition are applied may be any glass fiber produced from fiberizable heat softened glass, for example, the well known fiberizable glass compositions like “E-glass” and “621-glass”. Also, any more environmentally acceptable derivatives of “E-glass” and “621-glass” can be used such as low or free fluorine and/or boron fiberizable glass compositions.

[0024] The coating compositions may contain a solvent if needed. The solvent is used to drop the viscosity (cPs) of the coating solution to increase its sprayability. I prefer a viscosity ranging from 275-325 cPs. Usually, this requires the coating solution to contain 2-40 weight percent solvent depending upon the other materials present in the coating solution.

[0025] The length of the glass filaments and whether or not they are bundled into fibers and the fibers bundled in turn to yarns, ropes or rovings and the like are also not critical to the invention. However, in preparing the molding compositions of the present invention, it is convenient to use filamentous glass in the form of chopped strands of from about {fraction (1/32)} to about 2 inches long. The key is to provide shattering and shearing during processing, yet stopping short of considerable fragmentation occurring. Preferably, I use {fraction (1/16)} inch chopped roving.

[0026] The composition may be applied to the glass fibers by any method known to those skilled in the art. The glass fibers treated with the composition can be of any filamentary diameter known to those skilled in the art and the treated glass fibers can be gathered into one or more strands of any construction known to those skilled in the art. The composition can be prepared by adding the components sequentially or simultaneously to a desired amount of water or a fraction of the desired amount of water.

[0027] Other reinforcements that may be used with our coated chopped roving include carbon fibers, aramid fibers, KEVLAR, polyester and the like and even wood or other organic fibers. Preferred fillers of this type are milled glass fibers (hammer-milled) expanded polystyrene beads or ceramic microspheres (micro balloons).

[0028] The apparatus for drying the continuous strands may vary widely. Typically, I can use a drying chamber, heated rotary drum or electric, gas, infrared, ultraviolet, dielectric, microwave, fluidized bed dryers and the like. Preferably, I use hot air exhausted through a drying chamber as the continuous strands pass therethrough. Drying temperatures are dependent on the coating and strand I use.

[0029] Similarly, chilling may take place in a chamber, rotating drum, fluidized bed and the like. As previously stated, I prefer wrapping the roving around a chilled mandrel (−20° F.) before chopping them into appropriate lengths.

[0030] This thermosettable polyester composition may also optionally include pigments, flame retardants, surfactants, inert fillers such as talc, mica, etc. mold release agents and other well known processing fillers.

[0031] The mold may be of any type well known in the art. The mold may also contain various well known mold release agents such as waxes and the like on the surface in order to facilitate removal of the article from the mold.

[0032] The gel coat layer preferably has a smooth and shiny outer surface simulating the appearance of porcelain. This is accomplished by the surface of the mold upon which the thermosettable polyester resin composition is sprayed being smooth and polished.

[0033] The gel coat layer generally has a thickness of from about 10 to about 50 mils, preferably from about 35 to about 45 mils.

[0034] In the case of bath tubs and showers, the male portion of the mold generally is made of polished nickel. The key to my coating is not too much wet out of the chopped rovings. Once the coating is sheared and blended in the resin mix, mold takes place. Left in itself, the molding would exothern to 180° F. A key process step is to preheat the mold to 130° F. and then cool it during molding to maintain the 130° F. temperature. The polystyrene in the sheared coating helps dissolve the polyester resin.

[0035] The following formulations are provided to illustrate examples of the compositions of the present invention and are not intended to restrict the scope thereof. Amounts of material are in weight percent, unless otherwise expressly specified.

[0036] The formulas for the coating solutions had the following ranges. TABLE I Material Weight Percent Vinyl-Ester  30-60 MMA, methyl methacrylate   5-40 Styrene (<50 part H.Q.)   5-50 Cobalt .01-.3 DMA, diethylamine .01-.2 DMPT dimethyl-p-toluidine .05-.5 BYK-501, silicone free, air  .1-1.0 release agent Lexan bead, polycarbonate   5-50 Catalyst  .5-3 Solvent (used to drop cps and increase   2-40 spray ability), acetone

[0037] TABLE II Material Weight Percent Epoxy base resin  20-40 Hardener   5-20 De-air agent, BYK-501  .5-1.0 Polystyrene bead   5-50 Solvent   2-40

[0038] TABLE III Material Weight Percent Isophtalic Unsaturated Resin  30-60 MMA, methyl methacrylate   5-40 Styrene (<50 part H.Q.)   5-50 Cobalt .01-.3 DMA dimethylamine .01-.2 DMPT dimethyl-p-toluidine .05-.5 BYK-501  .1-1.0 Lexan bead   5-50 Catalyst  .5-3

[0039] The following examples further illustrate these coating solutions.

EXAMPLE I

[0040] Material Weight Percent Vinyl ester 50 MMA, methyl methacrylate 19.8 Styrene (<50 part H.Q.) 15 Cobalt .25 DMA, diethylamine .05 DMPT, dimethyl-p-toluidine .2 BYK-501 .6 Lexan bead, polycarbonate 10 Catalyst 2 Solvent (used to drop cps and increase 2.1 spray ability) (acetone)

EXAMPLE II

[0041] Material Weight Percent Epoxy base resin 36 Hardener 7.2 De-air agent, BYK-501 1.0 Polystyrene bead 20.0 Solvent (acetone) 34.8

EXAMPLE IIII

[0042] Material Weight Percent Isophtalic Unsaturated Resin 50.0 Styrene (<50 part H.Q.) 20.0 Cobalt .2 DMA .1 DMPT .2 BYK-501 .5 Lexan bead 12 Catalyst 2.0 Solvent (acetone) 15.0

EXAMPLE IV

[0043] E glass roving coated with the coating composition of Examples I, II and IIII were threaded through a series of threaders, eyelets and brakes. The glass traveling at 2-14 feet per second then was coated with the epoxy/polystyrene mixture. The glass now coated then was dried using a standard high intensity I.R. oven. After drying, the roving then was wrap around chilled mandrels (−20° F.) and chopped into an appropriate length of {fraction (1/16)} inch.

EXAMPLE V

[0044] The coated fibers of Example IV, after processing, then were introduced into the resin matrix of Table II in a ribbon blender. Downstream the fibers within the turbine mixer were then shattered and sheared for uniformity and mechanical strength. The epoxy of the coating composition dissolves into the resin during processing. The feet per minute of the matrix through the output lines, temperature of matrix, turbine pitch and RPM all influence the products integrity and appearance.

[0045] I then had compression molded panels made with the slurry premix of Example V.

[0046] In addition to these embodiments, persons skilled in the art can see that numerous modifications and changes may be made to the above invention without departing from the intended spirit and scope thereof. 

I claim:
 1. One or more fibers having at least a portion of their surfaces covered with an after coating composition wherein the after coating composition prevents the fibers from interacting with a plastic matrix and wherein the after coating composition is capable of being stripped or sheared from the fibers.
 2. One or more fibers having at least a portion of their surfaces covered with an after coating composition comprising a mixture of an epoxy resin and polystyrene, wherein the after coating composition is capable of being stripped or sheared from the fibers.
 3. Fibers according to claim 2 wherein the coating composition is a dried residue on the surfaces of the fibers.
 4. Fibers according to claim 2 wherein the epoxy resin is a reaction product of bisphenol A and epichlorohydrin.
 5. Fibers according to claim 2 wherein the polystyrene is homopolystyrene.
 6. Fibers according to claim 2 wherein the fibers are rovings, strands or yarns.
 7. Fibers according to claim 2 wherein the fibers are glass fibers.
 8. Fibers according to claim 2 wherein the fibers are glass fiber rovings.
 9. Fibers according to claim 2 wherein the coating composition is present on the fibers in an amount ranging from 1% to 15% by weight as a moisture reduced residue.
 10. Fibers according to claim 9 wherein the amount of coating composition ranges from 5 to 10 weight percent.
 11. Fibers according to claim 9 wherein the amount of coating composition ranges from 7% to 9% by weight.
 12. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Epoxy polymer 20-60 Styrene polymer  5-50


13. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Vinyl ester 30-60 Styrene  5-50


14. Fibers according to claim 13 wherein the coating composition also comprises: Material Weight Percent Methyl methacrylate 5-40 Polycarbonate 5-50 Solvent 2-40


15. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Epoxy resin 20-40 Polystyrene  5-50 Solvent  2-40


16. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Isophtalic Unsaturated resin 30-60 Styrene  5-50


17. Fibers according to claim 16 wherein the coating composition also comprises: Material Weight Percent Methyl methacrylate 5-40 Polycarbonate 5-50


18. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Vinyl ester 50 Methyl methacrylate 19.8 Styrene 15 Solvent 2.1


19. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Epoxy resin 36 Polystyrene 20.0 Solvent 34.8


20. Fibers according to claim 1 wherein the coating composition comprises: Material Weight Percent Isophtalic unsaturated resin 50.0 Styrene 20.0 Polycarbonate 12


21. A resin composition comprising a resin and the fibers of claim
 1. 22. A resin composition according to claim 21 wherein the resin is a thermoset resin.
 23. A resin composition according to claim 21 wherein the resin is a polyester resin.
 24. A resin composition according to claim 21 wherein the polyester resin is a foamed polyester.
 25. A premix slurry comprising the resin composition of claim 23 wherein the after coating composition is stripped or sheared from the fibers.
 26. A compression molded product comprising the resin composition of claim
 21. 27. A compression in molded product comprising the resin composition of claim
 24. 28. A compression molded product comprising the resin composition of claim
 25. 29. A process for coating one or more fibers having at least a portion of their surfaces covered, comprising the steps of: applying an after coating composition to the surfaces of the fibers, wherein the after coating composition prevents the fibers from interacting with a plastic matrix and wherein the after coating composition is capable of being stripped or sheared from the glass fibers; drying the coated fibers; and chilling the dried fibers.
 30. A process for coating one or more fibers having at least a portion of their surfaces covered, comprising the steps of: applying an after coating composition comprising a mixture of epoxy and polystyrene to the surfaces of the fibers, wherein the after coating composition is capable of being stripped or sheared from the glass fibers; drying the coated fibers; and chilling the dried fibers.
 31. A process according to claim 1 wherein the chilling is carried out at −20° F.
 32. A process according to claim 30 including the step of chopping the chilled fibers into appropriate lengths.
 33. A process for preparing a resin composition comprising the steps of admixing the fibers of claim 30 and a resin and subsequently stripping or shearing the after coating composition from the fibers after admixing with the resin.
 34. A process according to claim 33 wherein the admixing is carried out by blending.
 35. A process according to claim 33 wherein the shattering is carried out by tumbling.
 36. A process according to claim 30 including the step of the polystyrene of the coating composition dissolving the resin. 